Apparatus for annealing magnetic iron



4 Sheets-Sheet 1 H. A. FIELD APPARATUS FOR ANNEALING MAGNETIC IRON Filed March 24, 1948 June 12, 1951 June 12 1951 H. A. FIELD 2,556,962

A APPARATUS FOR ANNEALING MAGNETIC IRON Filed March 24, 1948 4 sh et -Sheet 2 A m U ---g:

INVENTOR HAJ /ELD i 4 Br ATTORNEY June 12, 1951 H, A, FIELD 2,555,952

APPARATUS FOR ANNEALING MAGNETIC IRON Filed March 24, 1948 4 Sheets-Sheet 5 Patented June 12, 1951 APPARATUS FOR ANNEALING MAGNETIC IRON Herbert A. Field, Hillside, Ill., assignor to Western Electric Company, Incorporated, New York, N. Y., a corporation of New York Application March 24, 1948, Serial No. 16,788

9 Claims.

This invention relates to an apparatus for heat treating metal parts in a protective atmosphere and more particularly to an apparatus for hydrogen annealing parts within a protective envelope of a neutral atmosphere.

In the processing of iron and other metal parts for use in electromagnetic devices, it is known that, by annealing the parts in an atmosphere of pure hydrogen gas, a substantial increase in certain magnetic properties of the parts may be obtained. However, because of the fact that free hydrogen may readily combine with the oxygen in the air to form an explosive mixture, its use involves an explosive and fire hazard.

An object of the present invention is to provide anapparatus for hydrogen annealing metal parts with a high degree of safety.

In one embodiment of the invention, there is provided a furnace having an inner chamber in which the parts to be annealed are placed and which is enclosed in an outer chamber in which the heating elements are located. Nitrogen gas is fed to the inner chamber to purge the atmosphere of air therein, which outflowing atmosphere is passed through a gas analyzer to indicate the state of purity or density of the nitrogen atmosphere in the inner chamber and, when the air has been completely purged from the chamber and the gas therein is substantially pure nitrogen, the gas analyzer will so indicate and cause visible and audible signals to be operated. Nitrogen is then: shut off from the inner chamber and hydrogen is flowed therein to purge the nitrogen gas which passes out from the inner chamber through the gas analyzer. Simultaneously with the shutting off of the nitrogen supply to the inner chamber, nitrogen is fed to the outer chamber for a predetermined period of time to purge the air therefrom and substitute an atmosphere of nitrogen therefor, which forms an envelope of protective inert gas around the inner chamber to prevent infiltration of air into the hydrogen filled inner chamber and to insure a neutral mixture either in the bell or in the hood in case of a leak in the hood. The gas analyzer, when the gas passing therethrough indicates that the gas in the inner chamber is pure hydrogen and has completely purged the nitrogen therefrom, closes a relay circuit to eifect a reduction in the rate of feed of hydrogen to the inner chamber. The closing of the relay circuit also effects the closing of a power switch to energize the heating elements of the furnace and to initiate the operation of a program controller unit for controlling the various levels of temperatures and the time at the various levels of temperatures to which the parts are subjected and for controlling the rate of cooling. After the parts have been heat treated and the parts have cooled to the proper point, the flow of hydrogen is cut off and the nitrogen is turned on to flush the inner chamber of all traces of hydrogen, after which the nitrogen is out off and the furnace is ready to be opened.

The invention will be more fully understood by reference to the following detailed description thereof and the accompanying drawings illustrating somewhat diagrammatically a preferred embodiment thereof in which Fig. 1 is a vertical central cross sectional View through the furnace;

Figs. 2 and 2a, together, comprise a diagrammatic view of the apparatus; and

Fig. 3 is a wiring diagram of the electrical control portion of the apparatus.

In the embodiment of the apparatus selected to illustrate the invention, a furnace 9 is provided comprising a hollow base H] enclosing a space H therein, a removable hood l2 adapted to fit on the top of the hollow base and form a gas-tight inner chamber 13 in which the parts IE to be annealed are placed, and a removable bell I6 adapted to fit on the base Ill over the hood I! to form agas-tight space I! around the hood, which space ll, together with the space H in the base, forms an outer chamber or envelope entirely enclosing the inner or heat-treating chamber l3.

The piece parts ii are placed on a perforated platform or grate [9-, which is mounted on the upper surface of the base IU of the furnace and is supported in spaced relation thereto by means of posts 20. The hollow base comprises a top wall 2!, a conically shaped wall 25 connected thereto, and a bottom wall 23. A skirt portion 2-"; formed on the conical Wall portion 25 is imbedded in sand 26 contained in a channel 22 formed on the upper outer edge portion of the lower wall 23 and this construction forms a substantially gas-tight seal between the walls 23 and 25. Extending downwardly from the lower portion of the wall 25 is a cylindrical wall or extension 28, from the lower edge of which extends a horizontal flange member 29. The flange member 28 supports an annular rubber gasket 3! and cooperates with the extension 28 and an annular member 39 of L-shaped cross section to form an annular conduit 32, disposed adjacent the gasket 3|, through which conduit a coolant o may be circulated to prevent the gasket 55 from becoming overheated.

The hood 52 comprises a cylindrical wall which is closed at the top by the curved wall and has on the lower edge thereof a flared skirt or wall portion from the lower end of which extends a cylindrical portion 38, terminating in an annular bead 39. Extending horizontally from the cylindrical portion 38 is a flange or sealing member ii having an annular groove for receiving an annular rubber gasket :52 and cooperating with an annular member hi to form an annular conduit :3, adjacent the gasket 2, through which a coolant may be circulated to prevent damage to the gasket from excessive heat. A plurality of clamping bolts 55, pivotally connected to the flange member 2t and engage able with the member ii, are provided to clamp the hood to base member.

The bell I5 comprises a cylindrical side wall 59, a top wall it and a narrow annular lower wall 41, from the inner edge of which projects an axially extending flange 38, terminating in an annular hollow bead or pipe t9. When the bell I6 rests on the furnace base 26 in its closed position, the annular pipe iii compresses the rubber gasket 42 to form a gas-tight seal between the lower edge of the hood I2 and the bell I6 and a coolant is circulated through the pipe 49 to prevent deterioration of the gasket due to excessive heat. The bell I5 is lined with a substantial thickness of refractory heat insulating material 5I5l and is provided with a plurality of vertically disposed circumferentially arranged cylindrical heating elements 52. An opening 53 is provided in the upper wall through which a pair of thermocouples 55 and 55 may be inserted into the chamber ll, and gas inlet and outlet pipes 5? and 59 are provided in opposite walls of the bell It at the lower and upper levels, respectively, of the bell I6 and the space H formed therein.

The base it is also provided with a substantial layer of refractory heat insulating material 53 supported on the lower wall 23 and in spaced relation to the upper wall 2! thereof, thus forming the space I I in the upper portion of the base II A plurality of heating elements are mounted in the space I I and inlet and outlet pipes 5i and 52 pass through the bottom wall 23 and the insulation 58 to permit the circulation of nitrogen gas into and out of the space it. An opening 5 is provided in the base in which a thermocouple (i5 is mounted to extend into the space H. A pipe 67, extending through the base IE and terminating at the upper surface thereof, establishes communication with the chamber E3 at a low level therein and a pipe 5%, passing through the base I0 and extending upwardly and then laterally across the upper end of the chamber is and hav ing openings in the lateral portion, establishes communication with the chamber at an upper level. The base Id of the furnace is mounted on a suitable support block, such as the block 8.

The pipe 5?, communicating with the inner chamber I3 of the furnace (Fig. 2), is connected to one end of a conduit or pipe line it, which, at its other end, is connected to a port H of a manually operated four-way or reversing valve '12. The reversing valve I2 has four portsli, I3, I4 and i5, and a rotatable core member, which is provided with passages therein for selectively establishing communication between adjacent pairs of ports. A conduit or supply line 36 extends from the port I3 of the reversing valve and has connected therein a pressure regulating valve 11 and a meter 78 and at its other end is connected to or formed into a manifold 19. A pair of branch lines BI and 82 are connected to the manifold I9 and are connected at a point 83 to, and form a part of, a hydrogen supply line 85, which is, in turn, connected to a suitable source of supply of hydrogen gas. The hydrogen supply line 85, adjacent the juncture of the branch lines, is provided with a manually actuated shutofi valve 87, a normally closed solenoid operated cutoiT valve 88, and a pressure switch 89. The branch line 8i has a gas flow regulating valve and a flow scope 9i connected therein and the branch line 82 has a flow control valve 52, a flow scope 93 and a normally closed solenoid operated cutoff valve 94 connected therein.

The pipe 68 to the inner chamber I3 of the furnace is connected to one end of a conduit or pipe line 95, which, at its. other end, is connected to the port 34 of the reversing valve '12. An exhaust line 96, connected to the port I5 of the reversing valve l2, has connected therein a back pressure valve 9! and a fire check valve 98 and is connected to a vent pipe I630 extending outside of the building in which the furnace is housed. A line GUI, connected to the exhaust line and forming a part thereof, is connected through branched end portions thereof to a pair of gas analyzers IE4 and Hi5, and line IE6 from the gas analyzers leads to the vent pipe I00.

The inlet pipe in communicating with the space Ii in the base of the furnace and the inlet pipe 5? in the bell I6 of the furnace are connected to the branched ends I68 and I09, respectively, of a nitrogen supply line E It. A portion of the branch ine I58 is flexible, to permit the bell I6 to be removed from and replaced on the base of the furnace. The line HE! has connected therein a pressure reducing valve H4, at flow control valve H5, a flow scope H6, a meter IN, a normally closed solenoid operated shutoif valve H8, and a manually operated shutoif valve I I9, and is connected at I28 to a main nitrogen supply line I2 I. Also connected to the main nitrogen supply line I2I at I 20 is a branch line E24, which is connected at its other end to the manifold I9 and has connected therein a manually operated shutoff valve I25, 2. pair of normally open solenoid operated shutoff valves I26 and i227, a how scope I28, and a fiow control valve I29, Connected to the branch line I24 between the valves I26 and I27 is an exhaust line ISI, which is connected to the vent pipe I630 and has connected therein a normally closed solenoid operated shutoif valve I32.

The outlet pipe 59 in the bell I6 of the furnace and the outlet pipe 62 in the base I0 are connected to branched ends of an exhaust line I35, which leads to the vent pipe iiiil and has a pressure regulating valve I36 and a pressure switch I3? connected therein.

Portions of the apparatus, such as the control valves, the pressure regulating valves, the gas meters, gas analyzers, flow scopes, et cetera, may be grouped together and mounted on a vertical panel or support 38, indicated in dotted lines in Fig. 2 and positioned in a convenient location adj acent the furnace 9.

It will be seen, from the description of the apparatus thus far, that the pipes 6'. and 58, lead-' ing to different levels in the inner chamber I 3 within the hood 56 are connected, respectively, by conduits it and. 95, to the reversing valve 52 and that the supply conduit l6 and the exhaust conduit 95 are also connected to the reversing valve '52 and, further, that the hydrogen I supply line 85, through s branches Ill and 82, and the nitrogen supply line I2I, through its branch I2 3, are connected to the supply conduit 16 at the manifold 19. Thus, with the shutoff valves 88 and 94 in the hydrogen supply line 35 closed and with the shutoff valves I25, I26 and I21 in the nitrogen supply branch line I24 open, and turning the reversible valve 12 to the position shown in Fig. 2, nitrogen gas is fed through the inlet pipe 61 into the lower end. of inner chamber I5 of the furnace to purge the atmosphere within the chamber. The atmosphere within the chamber is displaced by the nitrogen and is exhausted through the pipe 68 and the conduits connected thereto to the outer atmosphere, a portion of the exhaust gases being by-passed through the analyzers I66 and IE5 before being vented to the outside atmosphere. By closing the shutoff valves I 26, I21 in the nitrogen supply line and Opening the shutoff valves 81, '88 and 94 in the hydrogen supply line and rotating the reversing valve 12 one-quarterturn, hydrogen may be fed, through the pipe as, into the upper end of the inner chamber I3 of the furnace to purge the nitrogen atmosphere from the chamber. The nitrogen atmosphere is flushed from the inner chamber through the pipe I51 and the conduits conducting it to the vent IIID into the outside atmosphere and a portion of the gases being exhausted will pass through the gas analyzers I04 and I05 before being vented to the outside atmosphere. The back pressure valve '91 in the exhaust line 95 and the gas analyzers Iil4 I05 in the line It! insure a predetermined gas pressure in the inner chamber I3.

The gas analyzer I04 operates to indicate the density of nitrogen (.94) and the gases having a density ranging from I to .9 and the gas analyzer I05 operates to indicate the density of hydrogen (.4) and gases having a density ranging from .5 to .2. The gases, as they are exhausted from the chamber I3, are being continuously analyzed and the analyzers IQ-dI65 are continuously indicating the density of the gases in the chamber during the operation of the apparatus.

Nitrogen from the main supply line I2I is supplied through the lines H5, I08 and I59 and the pipes 6i and 51 to the base I!) and the bell I8 of the furnace. The outfiowing nitrogen in the base ID and the bell I6 is conducted through the outlet pipes 62 and 59, respectively, and the exhaust line I35 to the vent I93 and the pressure of the nitrogen atmosphere in the bell I5 and the base It is maintained at predetermined value by the back pressure regulating valve I36 in the line I35. The hydrogen gas, when flowing through the branch lines SI and 82, is controlled by the control valves Qi! and 92, respectively, and the rate of flow thereof is indicated by the fiow scopes SI and 93 and the volume passing through the line It is registered on the meter 18. In like manner, the flow of nitrogen through the branch line I24 may be regulated by the control valve I29 and indicated by the flow scope I28 and its volume indicated by the meter 18. The nitrogen passing through the branch line 'I If! is regulated by the valve II5 to control its rate of flow, which is indicated by the flow scope I I6, the volume of the gas being indicated by the meter ill, the pressure of the gas as it enters the furnace being regulated by the pressure regulating valve III, and the gas pressure in the base I6 and in the bell It being regulated by the back pressure valve I36.

The nitrogen supply line I2I (Fig. 2a) is con- 6. nected to a source of nitrogen supply I45 and, through a branch line I46, to an emergency or standby supply of nitrogen M1. The main and the emergency supplies of nitrogen, as disclosed herein, each comprises compressed nitrogen contained in a battery of cylinders connected to the supply lines in a conventional manner and having suitable pressure regulating valves associated therewith to reduce the high pressure therein to about fifteen pounds in the supply line I2I.

The pressure of nitrogen gas is further reduced in the line I 2: to four ounces by a pressure regulating valve I59, and, before the nitrogen is fed into the furnace, the pressure is still further reduced to 1". water gage by the previously described pressure regulating valve 11. Also connected in the nitrogen line IZI adjacent the pressure regulating valve I 59 is a pressure switch I52 and in a portion of the line adjacent the supply I45 are a pressure switch I54 and a normally closed shutofi valve I55. The branch line I46 is provided with a pressure switch I51 and 3, normally open solenoid operated cutoif valve I58.

The hydrogen supply line is connected to a main supply of hydrogen I6 and, through a line I6I, to an auxiliary supply I62. The main and auxiliary sources of hydrogen supply I BIJ and I 52 are shown herein as comprising a battery of tanks containing the compressed hydrogen have the conventional pressure reducing valve means to reduce the high pressure of the gas in the tank to approximately fifteen pounds in the line 85. The pressure of the hydrogen gas in the line' 85 is further reduced to four ounces by a pressure regulating valve I65 connected in the line 85 within the building housing the furnace and the hydrogen pressure is further reduced to 1" water gage before passing into the furnace by the aforementioned pressure regulating valve 11.

A pressure switch I61 and a vent line I68 are connected in the line 18 on the low pressure side of the pressure regulating valve I65 and a pressure regulating valve I69 in the line I68 is set to vent the hydrogen from the. supply line 85 if the pressure therein is raised a pre-' determined amount above its normal pressure. Adjacent the supply end, the line 85 is provided with check valve flash arresters I19 and,

at points where it enters the building and on.

the control panel I38, the line 35 is provided with fire check valves I1! and I12, respectively. A filter unit I14, a catalyst unit I15, and a dryer unit I16 are connected in the line 18. The hydrogen gas is filtered as it passes through the filter I14 and whatever oxygen is contained therein is combined with hydrogen in the cataylst unit I15 to form water, which is removed from the gas as it passes through the dryer unit I16 so that, when the hydrogen is supplied to the furnace, it is in a high state of dryness and purity.

The heating elements 52 of the furnace (Fig. 3) are connected to the secondary of a threephase transformer I11, the primary of which is connected, through electronic contactors I18- and a manually operated switch I19, to a threephase power line I853. The heating elements EU in the base I-J of the furnace are connected to the secondary of a transformer I82, the primary of which is connected, through an auxiliary contactor or switch I83, to a pair of conductors leading to the primary of the transformer II'i. A pair of wires eat from the power line I80 are connected, through a manually operated switch I35, to the primary of a transformer I86, the secondary of which supplies 110 volt current through a pair of lines I81 and I88 to various electrical control devices connected thereto.

The gas analyzer Hill has a pointer I98 movable across the scale I9 I graduated to read from .9 to 1 to indicate the densities of gases passing therethrough and having densities in this range. With nitrogen flowing into the inner chamber I3, the exhaust gases flowing therefrom into the anaylzer I94 cause the pointer I90 to move to the left and, when the pointer reaches the position .94, indicating a gas having a density or" approximately pure nitrogen, it actuates a switch I92 to close a secondary circuit of a transformer type relay 94. The primary of the relay I94 is connected by a switch I95 across the power line Nil-I88 and, when the switch I92 is closed, the relay I94 is actuated to close a pair of contacts I95, which are connected across the power line I8II88 and in series with the pressure switch I67, in the hydrogen supply line 85, the pressure switch 52 in the nitrogen supply line l2 I, the normally closed contacts 89fi of the pressure switch 89 in the hydrogen supply line, and a relay I99, which is connected in parallel with a signal lamp 209. Upon the closing of the contacts I95 by the relay IQAl of the anaylzer I64, the pressure switches I61 and 552 being closed, a circuit is completed to light the lamp 263 and energize tthe relay I53, which closes a pair of contacts I99I connected in series with an alarm bell 2% across the power lines Nil-48B. Thus, when the pointer I98 of gas anaylzer I04 is moved to the point .94 on the scale I9I in response to pure nitrogen gas passing through the anaylzer, the signal lamp 290 is lit and the alarm bell 2114 is rung to indicate that the nitrogen flowing into the inner chamber has completely purged the air therefrom and that the inner chamber is in condition to receive hydrogen preparatory to the annealing operation.

The operator may now close a push button switch 206 to close a circuit through the coils of the following solenoid actuated valves: the normally closed shutofi" valves 88 and 94 in the hydrogen lines 85 and 82, respectively, the normally closed shutofif valve H3 in the nitrogen branch line III], the normally open shut oil valves I26 and I27 in the nitrogen line I24, and the normally closed shutoff valve I32 in the vent line I3I. These valves are connected. in parallel with each other between the line I 88 and one side of the push button switch 208, the push button switch 286 being connected in series with the contacts the pressure switches I52 and I6? to the power line I81. Upon the closing the push button switch 265, the normally open valves I and I2! are actuated to cut off the flow of nitrogen gas in the branch line I24, the normally closed valve I32 in the vent line I3I is opened to vent any nitrogen that may pass through the shutoff valve I26, the normally closed valve H8 in the branch line IN! is opened to permit nitrogen gas to flow through the line I Ill and the branched ends I I18 and its thereof into the base Ill and the bell I6, and the normally closed valves 88 and 94 are opened to permit the iiow of hydrogen in the branch lines 81 and 82. With the valve 88 in the line as open, hydrogen pressure in the line will actuate th pressure switch 89 and move the two pairs of contacts 89I and 892 thereof to their opposite positions, thus opening the normally closed contacts 89 l and closing the normally open contacts 89-2. The contacts 89-4 are connected in parallel with the terminals of the normally open push button switch 236 and, upon being closed, the contacts 892 serve to maintain the circuit to the solenoid operated shutoff valves closed after the push button switch 2% has been actuated and while there is hydrogen pressure in the line 85. The contacts 89-4, upon being opened, break the signal circuit to effect the cutting ofi of the signal light 259 and the alarm bell 264.

To indicate that the reversing valve I2 should be moved to its other operating position when the gas supply to the inner chamber I3 has been changed from one gas to another, audible and visual signal means are provided which are energized or rendered operable in response to the closing of the push button switch 2%. A relay 256, connected between the push button switch 2% and the power line I88 is energized when the switch 2526 is closed and serves to actuate to their other positions a pair of contacts 2IIl-I and 259-4 in the signal control circuit. The contacts 2illi, which are normally closed, are connected to a limit switch 2M, and the contacts 2IIl2, which are normally open, are connected to a limit switch 2E5. The limit switches 2M and EMS are mounted to be actuated in response to the reversing movements of the reversing valve '52. Ihe limit switches 2M and Eli? are connected to the power line 68? and are arranged so that, the switch 2H3 is open and the switch H5 is closed when the reversing valve is set to establish communication between the supply conduit l6 and the conduit iii to pass nitrogen therethrough and when the reversing valve is turned to establish communication between the supply line I6 and the conduit 95 to pass hydrogen therethrough, the switch 2M will be moved to its closed position and the switch 2I5 to its open position.

The contacts 2IEll and 2Ill2 are connected to the power line I88 through a relay 2|? and a signal lamp 2I3 arranged in parallel with the relay. The rela 2H, when energized, closes a pair of contacts ZI'i-I arranged in parallel with the contacts I98-I to complete a circuit to and ring the alarm bell 224. In response to the closing of the push button switch 205 and the energization of the relay Bill, the contacts 2ifi2 will be closed, completing a circuit through the signal lamp H8 and the relay 2I'I, which rings the alarm bell 284. The operator, in response to the lighting of the signal lamp 2I3 and the ringing of the alarm bell 264, indicating that the reversing valve is in its improperposition, may rotate the valve to its other operative position, which movement serves to close the limit switch 254 and open the limit switch 2 I5, thus breaking the circuit to the signal light I8 and the alarm bell 204.

The gas analyzer I has a pointer 225 movable along a scale 2%, graduated to read from .2 to .5 to indicate the densities of gases passing 65 in the base it of the furnace.

ature control unit 243 has a second pair of contacts 24 5, which are normally open. The con- 9 through the analyzer and having densities within this range. When the pointer 225, in response to the gases passing through the analyzer, reaches the point .4 on the scale, indicating substantially pure hydrogen, it actuates a switch 221 in the secondary ircuit of a transformer type relay 2 255, the primary of which is connected by the switches 23d to the power lines i8l-l83, and thus effects the actuation to their opposite position of pairs of contacts 228-! and 228-4. The normally closed contacts 228-! are connected in series with the solenoid coil of the normally closed. valve 94 in the hydrogen line 82 and between the power line i88 and push button switch I95. The normally open contacts 2282 are connected in series with the relay 235 between the power line its and the push butt-on switch 205. Thus, when the pointer 225 of the gas analyzer has reached the point .4, indicating pure hydrogen is flowing in the inner chamber and has purged the nitrogen therefrom, the contacts 228i will be opened to break the circuit to the solenoid of the normally closed valve 94 which is returned to its closed position and shuts off the flow of hydrogen in the branch line 82 and thereby reduces the flow of hydrogen into the inner chamber i3 during the annealing of the parts.

Simultaneously with the opening of the contacts Z28l, the contacts 228-2 are closed to complete the circuit to energize a relay 235 which, upon energization, acts to close a contact 235! in an auxiliary contactor control circuit. The contacts 235! are connected in series with a solenoid coil 238, a switch 239, and a pair of normally closed contacts 2% across the power lines [8? and 88. The normally open switch 239 is closed by the bell l6 when the bell is lowered to its closed position on the base of the furnace. With the closing of the contacts 235l, the circuit is completed to energize the solenoid 238 and effect the closing of the contactor switch 583 for supplying current to the heating elements 69.

The normally closed contacts 2 in the' auxiliary contactor control circuit are actuated by and form a part of an excess temperature control unit 243, which is connected to the thermocouple The temperatacts 2:2! and Mt are connected in series, respectively, to signal lamps 245 and 246 across the power line Ti-483 and are actutaed to their opposite positions in response to the rise in tem- I perature in the chamber is above the maximum normal annealing temperature therein during the annealing operation. Thus, the excess temperature control unit 243 will act in response to an excess temperature in the base ii! to open the contacts 2M and break the circuit to the solenoid 2333, thereby allowing the contactor I83 to return to its open position and disconnect the heating elements from the power line. The lamp 245, which is lighted when the contacts 2 are closed, is deenergized when the contacts 24! are opened and the signal lamp 246 is lighted switch I31 in the exhaust line I35 will be actuits normal maximum operating value.

' tacts 25-8 are closed in response to the energizaated to close a circuit in the primary of a transformer-type relay 253. The secondary of the relay 25% is connected in series with the pressure switches. E52 and it? across the power line i8ll3%. The relay 250, when actuated, closes a pair of contacts Zed-i, which closes a circuit to a coil 253, which, in turn, when energized, closes a pair of contacts 25% to complete a circuit to a timing motor 255. The timing motor 255 acts to close a time delay switch 2% in an electronic contactor control circuit after a predetermined interval of time. The time delay switch 25? is connected across the power line i8ll88 and in series with pairs of contacts 258 and 259, a relay 2% and a normally closed pair of contacts 252 of an excess temperature control unit 263. With the contacts 258, 259 and 282 of the electronic contactor control circuit closed,.and upon closing of the time delay switch 251, the relay 268 will be energized to actuate the electronic contactors H8 and connect the heating elements 52 and till to the power line EBE.

The excess temperature control unit 253, which is similar in construction and operation to the temperature control unit 2413, is connected to the thermocouple 55 in the hell it and acts to open the contacts 2&2 and thereby effect the deener'gization of the relay 269, the opening of the electronic contactors H8 and the disconnection of the heating element 52 from the power lines I80 when the temperature in the hell it rises above The contion of the relay 238. The contacts 259 of the electronic contactor control circuit are actuated by relay 263 forming a part of a time and temperature control unit, generally indicated at 219. Th control unit 27 is connected across the power line Hal-M3 through switches 2ll 2ll and is connected to a thermocouple 56 in the bell it of the furnace. The various controls of the unit 2? are adapted to be set up according to'a predetermined program to control, through an operating cycle of the furnace, the temperatures, rate of change of temperature, and duration of the various temperatures in the inner chamber l3 of the furnace.

The pressure switch liil in the emergency nitrogen supply line its is connected in series with an alarm bell 2'l5 across the power line ESL-I88 and is held open by the gas pressure in the line and operates to close a circuit to ring the bell 215 when the pressure in the line ltt fails. The solenoid coil NOi58 of the normally open solenoid operated valve E53 in the emergency nitrogen supply line I is connected in series with a pair of contacts Ell across the power line Hill-488.

. The contacts 2?? are closed by the normally closed valve G in the main nitrogen supply line lZl when the valve is in its open position. The valve I55 of the Maxon type, which is manually movable to its open position and spring-actuated to its normally closed position, is held in its open position by a solenoid operated latch (not shown), the solenoid coil 2?.9 of which is connected across the power line Mil-488 in series with one pair of normally closed contacts l54| of the pressure switch Hi l in the nitrogen line l2l. The pressure switch E55 has a second pair of contacts l5d2, normally open, connected in series with a signal bell 283 across the power line l8'll88. In response to a reduction in the normal pressure of the nitrogen gas from the main supply hit, the pressure switch we will be-actuated. to close the pair of contacts l542, ringing the bell 283, and open the contacts I5 I-I, breaking the circuit to the solenoid 219, and releasing the valve I55, which is then springactuated to its closed position. The closing of the valve I55 shuts off the main supply of nitrogen and opens the contacts 2?? to break the circult to the normally open valve I58 and allow the valve to open and establish communication between the emergency nitrogen supply It! and the supply line i2i.

Operation When it is desired to anneal a batch of articles I5, the parts are placed in suitable perforated metal baskets or otherwise assembled and stacked on the grate I9 on the base It of the furnace and arranged thereon to permit free circulation of gas between the parts.

With the parts properly stacked on the base,

the hood l2 may be lowered thereon and clamped t the base and tested to insure a gas-tight juncture therewith, after which the "cell it may be lowered onto the base and over the hood to establish a gas-tight juncture therewith. Coolants are then circulated through the conduits 32, 43 and 49 to prevent damage to the rubber seals 3i and 62 from the heat of the furnace.

The switches I79 and I85 are now closed to connect the control circuits to the power line I80 and prepare the heating circuits to be connected to the power line and the manually operated valves 87 in the hydrogen line and H9, I25 and I55 in the nitrogen line are opened. Nitrogen gas is now free to flow through the branch line :24 and is fed into the lower end of the inner chamber I3 of the furnace to purge the air therein. The gases purged from the inner chamber i3 pass out through the pipe 68 and the exhaust conduits connected thereto, a portion of the gases passing through the gas analyzer I64, before it is vented to the outside atmosphere. When the air has been purged from the chamber I3, the gas analyzer EM- will indicate that pure nitrogen is flowing therethrough and will efiect the operation of the signal bell 2G4 and the signal lamp 265, indicating that no hydrogen is in the furnace.

The operator may then turn the reversing valve 12 to its other position to connect the gas supply line To to the pipe 68 at the upper end of the chamber 53 and the operator may close the push button switch 2% to actuate the various control valves and effect the cutting off of the nitrogen gas to the inner chamber I3, the feeding of hydrogen gas to the inner chamber to purge the nitrogen therein, and the feeding of nitrogen to the base I0 in the bell IS. The hydrogen flowing in at the upper end of the chamber I3 purges the nitrogen therefrom, which is exhausted through the pipe El and the exhaust conduits connected thereto, a portion of the gases being exhausted passing through the gas analyzer I05. When the nitrogen is substantially completely purged from the inner chamber, the gas analyzer I 05 will indicate substantially pure hydrogen flowing therein and will effect the closing of the valve 94 in the hydrogen branch line 82 to reduce the rate of feed of hydrogen into the inner chamber during the annealing period and also effect the closing of the contactor I83 to connect the heating elements 66 to the main heating circuit. The nitrogen flowing in the outer chamber actuates the pressure switch I31 in the exhaust line I35 and effects, after a predetermined time delay, the actuation of the electronic contactors I18 to con- 12 nect the main heating elements 52 and the auxiliary elements 60 to the power line I80. The furnace is thus heated and the temperature thereof is controlled through a cycle of operation by the time and temperature control unit 210.

On completion of the annealing of the parts, the operator may close the manually operated valve 8! in the hydrogen line 85, which cuts off the hydrogen gas to the chamber I3 and restores the pressure switch St to its normal position to effect the operation of the signal bell 264 and the signal light 2% and also the breaking of the circuits to the solenoid operated control valves, thereby restoring the control valves to their normal operating positions to cut off the flow of hydrogen to the inner chamber and feed nitrogen to the inner chamber of the furnace and also cut off nitrogen to the outer chamber. When the pressure switch 89 is restored to its normal position, it cuts oi the current to the relay 2I0, thus closing the contacts 2I0-I and, with the reversing valve I2 in a position to feed gas into the upper end of the inner chamber I3, the switch 2M is closed and the signal lamp H8 is lighted and the signal bell 284 is rung. The operator may then reverse the valve 12, thereby cutting off the signal lamp 2I8 and the bell 204. When the hydrogen gas has been thoroughly flushed from the chamber I3 and pure nitrogen is flowing therethrough, as indicated by the gas analyzer I04 and the signal elements 205 and 204, the manually operated valve I25 may be closed to shut oif the supply of nitrogen to the furnace. After the parts have been sufficiently cooled, the furnace may be opened and the parts removed therefrom.

In th event that the main supply I60 of hydrogen gas should fail during the operation of the furnace, the reduction in pressure would operate to open the pressure switch I61 in the hydrogen line and break the circuits to the various control valves, thus restoring them to their normal positions and shutting off the feed of hydrogen to the inner chamber, shutting off the feed of nitrogen to the outer chamber, and feeding nitrogen into the inner chamber to purge the hydrogen therefrom. With the opening of the pressure switch I51, the relays 2 I 0 and 235 are deenergized, which action of the relay 2Ill closes the contact 2I0I to operate the signal light 2I8 and the alarm bell 204 and, upon deenergization of the relay 235, the electronic and auxiliary contactors I18 and I83 are opened to disconnect the heating elements from the power line. The operator may then cut in the emergency supply I62 of hydrogen and the pressure thereof will close the pressure switch I61, after which the operator may press the push button 256 to reinitiate the hydrogen feeding portion of the gas feeding cycle of operation. The remaining portion of the cycle will be the same as previously described, with the nitrogen being cut off from the inner chamber, the hydrogen being fed to the inner chamber, and nitrogen being fed to the outer chamber, and after the hydrogen has flushed the nitrogen from the inner chamber and nitrogen is flowed into the outer chamber for a predetermined length of time, the heating elements are reconnected to the power supply to continue the heating of the furnace.

If the main supply I45 of the nitrogen gas should fail, the pressure switch I54 would be actuated to close the contacts I54-2 and operate the signal bell 283 and the contacts I54I would be open to and release the valve I55. The valve I55 would return to its normally closed position 13 and open the contacts 211 and break the circuit to the valve I58 in the emergency supply line I46, thus restoring the valve to its normally open position and connecting the emergency supply M1 to the supply line Hi.

In case of failure of power, the solenoid operated control valves mounted on the panel would be restored to their normal operating conditions, cutting ofi the supply of hydrogen to the inner chamber, cutting off the nitrogen to the outer chamber, and establishing communication between the inner chamber and the nitrogen supply line I21. The Maxon valve I55 in the main supply line will close to cut off the main supply of nitrogen gas and the valve [58 in the emergency supply line I46 will be restored to its open position, thus allowing the emergency supply of nitrogen gas to flow into the inner chamber of the furnace and flush the hydrogen therefrom. Thus, even though power failure occurs and the alarm bells and light signals cannot operate to signal the operator, the safety of the apparatus and the operator is assured by the automatic purging of the hydrogen from the inner chamber of the furnace, thus eliminating the fire and explosive hazard inherent in the use of hydrogen gas.

It is to be understood that the above-described arrangements are simply illustrative of the application of the principles of the invention. Numerous other arrangements may be readily devised by those skilled in the art which will embody the principles of the invention and fall within the spirit and scope thereof.

What is claimed is:

1. In a hydrogen annealing apparatus, a furnace having an inner chamber for receiving parts to be annealed and an outer chamber enclosing said inner chamber, outlets from said chambers, conduit means from said chambers to a sup-ply of nitrogen, conduit means from said inner chamber to a supply of hydrogen, electrically operated valve means in said conduit means having a normal position operable to shut off the flow of nitrogen to the outer chamber and the flow of hydrogen to the inner chamber and to establish a flow of nitrogen to the inner chamber to flush the atmosphere therefrom, a gas analyzer connected to the outlet from said inner chamber for indicating the relative densities of the gases purged from said inner chamber and having a control switch operable in response to the flow of substantially pure nitrogen therein, means including a switch operable in cooperation with said control switch to connect said electrically operated valves to a source of power to actuate said valve means to another position to shut off the flow of nitrogen and establish a how of hydrogen to said inner chamber and to establish a flow of nitrogen to said outer chamber, electrical heating elements in said outer chamber, and means to connect said heating elements to a source of power.

2. In a hydrogen annealing apparatus, a furnace having an inner chamber for receiving parts to be annealed and an outer chamber enclosing said inner chamber, outlets fromsaid chambers, conduit means from said chambers to a supply of nitrogen, conduit means from said inner chamber to a supply of hydrogen, electrically operated valve means in said conduit means having a normal position operable to shut off the nitrogen to the outer chamber and hydrogen to the inner chamber and to feed nitrogen to the inner chamber to flush the atmosphere there- All from, a gas analyzer connected to the outlet from said inner chamber for indicating the relative densities of the gases purged from said inner chamber and having a control switch operable in response to the flow of substantially pure nitrogen therein, means including a manually actuable switch operable in cooperation with said control switch in said gas analyzer to actuate said valve means to another position to shut off the nitrogen to the inner chamber and feed hydrogen to said inner chamber and nitrogen to said outer chamber, signal means, signal actuating means operable under control of said control switch in said gas analyzer to actuate said signal means to indicate the flow of substantially pure nitrogen in the inner chamber and operable in response to the actuation of said means for actuating said valves to terminate the actuation of said signal, heating elements in said outer chamber, and means to connect said heating elements to a source of power.

3. In a hydrogen annealing apparatus, a furnace having an inner chamber for receiving parts to be annealed and an outer chamber enclosing said inner chamber, outlets from said chamchamber and to shut off the hydrogen to the inner chamber and nitrogen to the outer chamber, a gas analyzing means connected to the outlet from said inner chamber for indicating the relative densities of the gases exhausted from said inner chamber and having a first control switch'operable in response to the flow of substantially pure nitrogen therein and a second control switch operable in response to the flow of substantially pure hydrogen therein, actuating means including a manually actuable switch operable in cooperation with said first control switch to connect said electrically operated valve means to a source of power to actuate said valve means to another position to shut off the flow of nitrogen to said inner chamber and to feed hydrogen to the inner chamber and nitrogen to the outer chamber, electrical heating elements in said outer chamber, and means operable in response to the actuation of said second control switch for connecting said heating elements to a source of power.

4. In a heat treating apparatus, a furnace having an inner chamber for receiving parts to be heat treated and an outer chamber enclosing said inner chamber, exhaust outlets from said inner and said outer chambers, conduit means from said inner chamber to a supply of hydrogen and from said inner and said outer chambers to a supply of nitrogen, electrically operated valve means in said conduit means having a normal position operable to shut oii the nitrogen to the outer chamber and the hydrogen to the inner chamber and to feed nitrogen to the inner chamber, a gas analyzing means connected to the exhaust outlet of said inner chamber for continuously analyzing the gas exhausted from said inner chamber and having a first control switch openable in response to the flow of substantially pure nitrogen in said analyzing means and having a second control switch operable in response to the flow of substantially pure hydrogen in said analyzing means, valve actuating means including a switch operable in cooperation with said first control switch to actuate said valve means to another position to shut oi? the nitrogen and feed hydrogen to the inner chamber and nitrogen to the outer chamber, signal means, signal actuating means operable under control of said first control switch to actuate said signal means to indicate the flow of substantially pure nitrogen in the inner chamber and operable in response to the actuation of said valve actuating means to terminate the actuation oi" said signal means, heating elements in said outer chamber, and means including a time delay device operable under control of said second control switch to connect the heating elements to a source of power after the lapse of a predetermined interval of time.

5. In a hydrogen annealing apparatus, a furnace having an inner chamber for receiving parts to be annealed and an outer chamber enclosing said inner chamber, outlets from said chambers, conduit means from said outer chamber to a supply of nitrogen, conduit means from said inner chamber to a supply of hydrogen, conduit means from said inner chamber having a branch line connectible to a main supply of nitrogen and another branch line connectible to an emergency supply of nitrogen, electrically operated control valves in said conduit means having a normal position operable to feed nitrogen to the inner chamber and shut off hydrogen to the inner chamber and nitrogen to the outer chamber, gas analyzing means connected to the outlet from said inner chamber for receiving the atmospheres purged therefrom and having a switch control means operable in response to the flow of substantially pure nitrogen therein, actuating means including a manually operated switch operable in cooperation with said switch control means for connecting said electrically operated valve -means to a source of power for actuating said valve means to another position to shut off the nitrogen to said inner chamber and feed hydrogen to the inner chamber and nitrogen to the outer chamber, a normally closed auxiliary valve manually actuable to open position and having electrically operated means for holding said valve in open position connected in said branch line between said electrically operated control valve means and the main supply of nitrogen and electrically connected to a source of power to maintain said auxiliary valve open during the normal operation of the apparatus, and an electrically operated normally open auxiliary valve, connected in the other branch line between said electrically operated control valve means and the emergency nitrogen supply and electrically connected to said source of power for maintaining said normally open auxiliary valve closed during the normal operation of the apparatus, said auxiliary valves being operable in the event of power failure to cut off the main nitrogen supply and cut in the emergency nitrogen supply.

6. In a hydrogen heat treating apparatus, a furnace having an inner chamber for receiving parts to be treated and an outer chamber enclosing the inner chamber, outlets from said chambers, conduit means from the inner chamber to a supply or nitrogen, conduit means from the outer chamber to a supply of nitrogen, conduit means from the inner chamber to a supply of hydrogen, valve means in said conduit means having a normal position operable to feed nitrogen to the inner chamber to flush the atmosphere therefrom and to shut ofi hydrogen to the inner chamber and nitrogen to the outer chamber, gas

analyzing means connected to the outlet from said inner chamber for receiving the atmospheres exhausted therefrom and having a first switch control means operable in response to the flow of substantially pure nitrogen therein and a second switch control means operable in response to the flow of substantially pure hydrogen therein, pressure responsive means in each of said conduit means to said inner chamber, a first actuating means including a manually actuated switch operable in cooperation with said first switch control means and said pressure responsive means for actuating said valve means to another position to shut 01f the nitrogen to the inner chamber and feed hydrogen to the inner chamber and nitrogen to the outer chamber, said pressure responsive means being operable to render said first actuating means eiiective or ineffective in response to variations in gas pressures in said conduit means to said inner chamber above and below, respectively, predetermined values, electrical heating means in said outer chamber, a pressure switch responsive to the gas pressure in said outer chamber, and a second actuating means operable in response to the actuation of said second switch control means in said gas analyzer and in cooperation with said pressure switch for electrically connecting said heating means to a source of power, said pressure switch being operable to render said second actuating means effective or ineiiective in response to variation in gas pressure in said outer chamber above or below, respectively, a predetermined value.

7. In a heat treating apparatus, a furnace having an inner chamber for receiving parts to be treated and an outer chamber enclosing said inner chamber, an outlet for said outer chamber, a first conduit means connecting said outer cila nber to a supply of nitrogen, a second conduit means connectibie to a supply of hydrogen and a supply of nitrogen and having a pair of end portions communicating with the upper and lower ends, respectively, of the inner chamber, electrically operated valve means in said conduit means having a normal first position operable to shut off the nitrogen to the outer chamber and the hydrogen to the inner chamber and to feed nitrogen to the inner chamber to flush the atmosphere therefrom, a reversing valve interconnecting said second conduit means and the p r end portions thereof, said reversing valve having outlet port and being operable in a position o establish communication between said conduit means and one of said pair of end portions and between said outlet port and the other of said pair of end portions whereby nitrogen may be fed into the inner chamber at the lower end and the atmosphere therein exhausted from the upper thereof, means for actuating d reversing valve to a second position to estabn' h coirmunicaticn between said conduit means and the other of said pair or" end portions and between said outlet port and said one of said pair of end portions whereby hydrogen may be fed, into the upper end of the chamber and the atr -osphere exhausted through the lower end thereof, a gas analyzing means connected to the outlet densities of the g .ses passing through said inner chamber and having switch control means opere in response to the flow of substantially pure gen therethrough, electrically operated sign means, means operable in response to the actuation of said switch control means for actuating said signal means to indicate the flow of substantially pure nitrogen in the inner chamber, actuating means including a manually actu-.

able switch operable in cooperation with said switch control means for connecting said electrically operated valve means to a source of power to actuate said valve means to a second position to shut off the nitrogen to the inner chamber and to feed hydrogen to the inner chamber and nitrogen to the outer chamber, means operable in response to the actuation of said electrically operated valves to said second position to shut off said signal means, and signal means associated with said actuating means and including switch means actuated by said reversing valve for indicating the relative positions of the reversing valve and said electrically operated valve means.

8. In a hydrogen heat treating apparatus, a furnace having an inner chamber for receiving parts to be treated and an outer chamber enclosing said inner chamber, outlets from said chambers, conduit means connecting the inner chamber to a supply of hydrogen, conduit means connecting said inner chamber to a supply of nitrogen, conduit means connecting said outer chamber to a supply of nitrogen, solenoid actuated valve means in said conduit means having a normal position operable to feed nitrogen to said inner chamber and to shut off hydrogen to the inner chamber and nitrogen to the outer chamber, a gas analyzing means connected to the outlet from said inner chamber for indicating the relative densities of the atmospheres exhausted from said inner chamber and having a first control switch means operable in response to the flow of substantially pure nitrogen therein and having a second control switch means operable in response to the flow of substantially pure hydrogen therein, electrically operated signal means operable under control of said first control switch means to indicate the flow of substantially pure nitrogen in said inner chamber,

supply, and actuating means operable in response to actuation of said second control switch means to actuate said flow regulating valve means to another position for reducing the rate of flow of hydrogen to said inner chamber.

9. In a hydrogen heat treating apparatus, a furnace having an inner chamber for receiving parts to be treated and an outer chamber enclosing the inner chamber, outlets for said chambers, conduit means from said inner chamber to a supply of hydrogen, conduit means from said inner chamber and said outer chamber to a supply of nitrogen, electrically operated valve means in said conduit means having a normal position operable to feed nitrogen to the inner chamber and to shut off the hydrogen to the inner chamber and the nitrogen to the outer chamber, gas analyzing means connected to the outlet from said inner chamber for indicating the densities of the gases exhausted from said inner chamber and having a first control means operable in response to the fiow of substantially pure nitrogen therein and having a second control means operable in response to the flow of substantially pure hydrogen therein, signal means operable under control of said first control means to signal the flow of substantially pure nitrogen in the inner chamber, means operable in cooperation with said first control means of said gas analyzing means to connect said electrically operated valve means to a source of power to actuate said valve means to another position to effect the shutting oil of nitrogen to said inner chamber and the feeding of hydrogen to the inner chamber and nitrogen to the outer chamber, said conduit means to said hydrogen supply having a pair of branches for dividing the flow of hydrogen from said hydrogen supply to said inner chamber, flow valves in said branches for controlling the rate of flow of hydrogen therein, an electrically operated shut off valve in one of said branches, electrical heating means for heating the inner chamber, and actuating means operable under control of said second control means for connecting the heating means and the electrically operated valve in said branch line to a source of power to cause the heating of the inner chamber and the actuation of said valve in said branch to shut off the flow of hydrogen in said branch line.

, HERBERT A. FIELD.

REFERENCES CITED I The following references are of record in the file of this patent:

UNITED STATES PATENTS 

1. IN A HYDROGEN ANNEALING APPARATUS, A FURNACE HAVING AN INNER CHAMBER FOR RECEIVING PARTS TO BE ANNEALED AND AN OUTER CHAMBER ENCLOSING SAID INNER CHAMBER, OUTLETS FROM SAID CHAMBERS, CONDUIT MEANS FROM SAID CHAMBERS TO A SUPPLY OF NITROGEN, CONDUTI MEANS FROM SAID INNER CHAMBER TO A SUPPLY OF HYDROGEN, ELECTRICALLY OPERATED VALVE MEANS IN SAID CONDUIT MEANS HAVING A NORMAL POSITION OPERABLE TO SHUT OFF THE FLOW OF NITROGEN TO THE OUTER CHAMBER AND THE FLOW OF HYDROGEN TO THE INNER CHAMBER AND TO ESTABLISH A FLOW OF NITROGEN TO THE INNER CHAMBER TO FLUSH THE ATMOSPHERE THEREFROM, A GAS ANALYZER CONNECTED TO THE OUTLET FROM SAID INNER CHAMBER FOR INDICATING THE RELATIVE DENSITIES OF THE GASES PURGED FROM SAID INNER CHAMBER AND HAVING A CONTROL SWITCH OPERABLE IN RESPONSE TO THE FLOW OF SUBSTANTIALLY PURE NITROGEN THEREIN, MEANS INCLUDING A SWITCH OPERABLE IN COOPERATION WITH SAID CONTROL SWITCH TO CONNECT SAID ELECTRICALLY OPERATE VALVES TO A SOURCE OF POWER TO ACTUATE SAID VALVE MEANS TO ANOTHER POSITION TO SHUT OFF THE FLOW OF NITROGEN AND ESTABLISH A FLOW OF HYDROGEN TO SAID INNER CHAMBER AND TO ESTABLISH A FLOW OF NITROGEN TO SAID OUTER CHAMBER, ELECTRICAL HEATING ELEMENTS IN SAID OUTER CHAMBER, AND MEANS TO CONNECT SAID HEATING ELEMENTS TO A SOURCE OF POWER. 